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Plague Overview • • • • • • • Organism History Epidemiology Transmission Disease in Humans Disease in Animals Prevention and Control Center for Food Security and Public Health Iowa State University - 2004 The Organism Yersinia pestis • Family Enterobacteriaceae − Gram negative coccobacillus, pleomorphic − Aerobic, facultative anaerobic, and facultative intracellular • Several plasmids and virulence factors − F1, murine exotoxin, LPS endotoxin, coagulase, pesticin, plasminogen activator Center for Food Security and Public Health Iowa State University - 2004 Yersinia pestis • Destroyed by − Sunlight − Desiccation • Survival −1 hour in air − Briefly in soil − 1 week in soft tissue − Years when frozen Center for Food Security and Public Health Iowa State University - 2004 History Brief History of Plague • 540-590 AD: Justinian’s pandemic − 10,000 deaths per day − Fall of the Roman Empire • 1346~1400: Black Death pandemic − Quarantine − 1/3 of European population died − Fall of the feudal system • 1665: Great Plague of London Center for Food Security and Public Health Iowa State University - 2004 “Ring Around The Rosy A Pocket Full Of Posies Ashes, Ashes All Fall Down” Center for Food Security and Public Health Iowa State University - 2004 Discovery • • 1894: Hong Kong epidemic Alexandre Yersin − Gram negative − Bacillus • 1896 − Developed antiserum Center for Food Security and Public Health Iowa State University - 2004 United States • 1899: Hawaii − From ship rats to sylvatic rodents − Spread throughout the western U.S. • 1924: Los Angeles − Last person-to-person case − 32 pneumonic cases • 31 deaths Currently established in southwest Center for Food Security and Public Health Iowa State University - 2004 Plague as a Disease • • • Class 1 quarantinable disease (WHO) CDC Division of Quarantine Reportable disease Center for Food Security and Public Health Iowa State University - 2004 Transmission Transmission • • Flea bite (78%) Direct animal contact (20%) − Tissues, body fluids, scratches, bites − Enters through break in skin • • Aerosol (2%) Human cases − April-November (93%) − Increased activity of fleas and hosts Center for Food Security and Public Health Iowa State University - 2004 Flea Vectors • • • Can live off host for months Many species can serve as vector Oropsylla montana − Rock and California ground squirrels, prairie dogs − Most important flea vector in U.S. • Xenopsylla cheopis − Epidemics in Asia, Africa, South America Center for Food Security and Public Health Iowa State University - 2004 Flea Transmission • 27°C (80°F) − Blood clots in gut of flea − Y. pestis trapped − Transmission occurs more readily • 27°C − Blood clot in gut of flea dissolves − Organism passes through − Transmission less likely Center for Food Security and Public Health Iowa State University - 2004 Epidemiology Where Are Cases Found? • Southwest (87%) − Northern New Mexico − Southern Colorado − Northern Arizona − California • 1925-1964 − ~2 • cases/yr Since 1970 − ~13 cases/yr Center for Food Security and Public Health Iowa State University - 2004 Plague in the U.S.: 2002 45 40 Reported Cases 35 30 25 20 15 10 5 0 1972 1977 1982 1987 1992 1997 2002 Year MMWR Center for Food Security and Public Health Iowa State University - 2004 Center for Food Security and Public Health Iowa State University - 2004 Epidemiology in Nature • • • Sylvatic (wild) Urban (domestic) Reservoirs − Rock squirrels − Ground squirrels − Prairie dogs − Mice, Voles − Others Dr. Lloyd Glenn Ingles © California Academy of Sciences Center for Food Security and Public Health Iowa State University - 2004 Sylvatic Plague • Enzootic Steady level in rodent populations − Low death rates − • Epizootic Large die-offs fleas change hosts − Amplifying hosts − Prairie dog, ground squirrels, rock squirrels, woodrats, chipmunks Expansion into human occupied areas − Greatest threat to humans − Center for Food Security and Public Health Iowa State University - 2004 Robert B. Crave. Plague. Infectious Diseases, 5th ed. J.B. Lippincott Co. 1994. Center for Food Security and Public Health Iowa State University - 2004 Urban Plague • • Infected fleas or rodents move to urban area Commensal (domestic) rodents infected • • Roof rat, Norway rat Rapid die off Fleas seek new host − Domestic • cats or humans Poverty, filth, homelessness Center for Food Security and Public Health Iowa State University - 2004 Disease in Humans Human Disease • Continuum of illness − Bubonic − Septicemic − Pneumonic Primary Secondary Center for Food Security and Public Health Iowa State University - 2004 Bubonic Plague • • • 80-90% of cases Incubation: 2-6 days Clinical signs − Fever, malaise, chills, headache − Bubo: swollen, painful lymph node − vomiting, abdominal pain, nausea, petechiae • Mortality (untreated): 50-60% Center for Food Security and Public Health Iowa State University - 2004 Septicemic Plague • • Systemic spread Clinical signs − Similar to bubonic, plus − Prostration, circulatory collapse, septic shock, organ failure, hemorrhage, DIC − Necrosis of extremities • Microthrombi blocking capillaries Mortality (untreated): 100% Center for Food Security and Public Health Iowa State University - 2004 Pneumonic Plague • • • • Incubation: 1-6 days Primary - Y. pestis inhaled Secondary - septicemic form spreads Clinical signs − Fever, chills, headache, septicemia − Respiratory distress, hemoptysis • Person-to-person possible Center for Food Security and Public Health Iowa State University - 2004 Diagnosis • • • • Isolation of organism Fourfold rise in antibody titer Single titer of >1:128 Differential diagnoses − Tularemia − Hantavirus − Streptococcus − Staphylococcus aureus Center for Food Security and Public Health Iowa State University - 2004 Treatment • With early treatment – Survival ~100% • Supportive Antibiotics • − Aminoglycosides Streptomycin, kanamycin − Doxycycline, tetracycline, chloramphenicol − Penicillins and cephalosporins are NOT effective Center for Food Security and Public Health Iowa State University - 2004 Human Case • New York, 2002 − Married couple from New Mexico − Fever, unilateral inguinal adenopathy − Bubonic plague diagnosed − Antibiotic treatment − Deteriorated (septicemic spread) − Sent to ICU − Recovered after 6 weeks Center for Food Security and Public Health Iowa State University - 2004 Importance of Case • NMDPH and CDC investigation − Trapped rodents and fleas around home − Y. pestis isolated • Importance − Plague out of endemic area Should raise suspicions − Prompt detection important Center for Food Security and Public Health Iowa State University - 2004 Animals and Plague Animals • Many found serologically positive − • Bears, bobcats, badgers, fox, ringtails, skunks, Mountain lion, deer, African elephant, African buffalo, camel, coyote, more … Rodents − Most • die readily from infection Farm animals and dogs − Very resistant to disease − May be incubating at time slaughter of Human risk Center for Food Security and Public Health Iowa State University - 2004 Animal Sources of Human Infection in U.S. (319 cases) 1970 -1993 18 20 109 110 14 1 23 24 Undetermined Carnivores Rabbits Antelope Prairie Dogs Rock Squirrels CA Ground Sq. Other Squirrels Center for Food Security and Public Health Iowa State University - 2004 Carnivore Source of Human Plague Infection, 1970-98 25 23 20 15 10 4 5 0 Cat Bobcat 2 Coyote 2 1 Gray Fox Badger Center for Food Security and Public Health Iowa State University - 2004 Cats and Plague • • No human cases from cats prior to 1977 By 1998 − 23 • • cases - 5 fatal Cats develop severe illness and die Can transfer disease to humans − Owners, veterinarians or staff − Pneumonic, fleas, bite, scratch Center for Food Security and Public Health Iowa State University - 2004 Cats and Plague • Clinical signs − Severe illness − Signs mimic human illness − Bubonic, septicemic, pneumonic − Fever, lethargy, anorexia − Lymphadenopathy Submandibular, cervical, others − DIC, death Center for Food Security and Public Health Iowa State University - 2004 Cats and Plague • Diagnosis − Confirmatory Fourfold rise in titer Isolation of organism − Presumptive Staining of specimen − Flea • testing Treatment − Aminoglycosides, tetracyclines Center for Food Security and Public Health Iowa State University - 2004 Cats: Experimental Infection • 16 cats − Each fed a plague infected mouse − All showed illness by day 3-4 − Lymphadenopathy by days 4-6 • • 6 cats died (37.5%) 75% − Blood culture positive − Culture positive throat/oral cavity Center for Food Security and Public Health Iowa State University - 2004 Cat to Human Case • New Mexico, 1977 − • 6 yr. old boy September 6 Fever, chills, vomiting, bilateral axillary pain − Insect bites & scratches on arms − Hospitalized with delirium − • September 8 − Needle aspirate of lymph node − Positive on staining and FA for plague IV antibiotics Center for Food Security and Public Health Iowa State University - 2004 Case • • • • Improved, fever continued for 8 days Buboes incised & drained on day 13 Released on day 16 History − Grandfather Fed to cats and dogs − Boy shot rabbits took one cat home Bit and scratched him Cat later died of plague Center for Food Security and Public Health Iowa State University - 2004 Dogs and Plague • Rarely show signs − Fever, lethargy, oral lesions, lymph node lesions • • • May seroconvert May carry infected fleas Diagnosis and treatment − Same • as cats Sentinels Center for Food Security and Public Health Iowa State University - 2004 Prevention and Control Prevention and Control • Isolate infected animals − Limit number of people in contact − Personal protection • Surgical mask, gloves, eye protection Flea control − Dogs and cats Spring to fall − Premise Center for Food Security and Public Health Iowa State University - 2004 Prevention and Control • • Prevent roaming or hunting of pets Rodent control − Eliminate rodent habitat around home Brush, food sources, firewood, junk − Undertaken • • only after insecticide use Insect repellents for skin & clothes Insecticide use in epizootic areas Center for Food Security and Public Health Iowa State University - 2004 Center for Food Security and Public Health Iowa State University - 2004 Prevention and Control • • Public health education Prophylactic antibiotics − Plague outbreak/flea bites − Handled infected animal − Close contact with plague case • Vaccine − Live and killed developed − No longer available in the U.S. Center for Food Security and Public Health Iowa State University - 2004 Prevention and Awareness • Report suspected animal cases − State health department − State veterinarian − Animals may serve as sentinels • Education of clients and public − Risks, • transmission, prevention Take precautions in enzootic and epizootic areas Center for Food Security and Public Health Iowa State University - 2004 Plague as a Biological Weapon • 1970 WHO estimate − 50 kg agent on city of 5 million 150,000 pneumonic cases • 36,000 deaths 80,000-100,000 hospitalized 500,000 secondary cases − Up to 100,000 deaths total Center for Food Security and Public Health Iowa State University - 2004 Additional Information • CDC - Division of Vector-borne Infectious Diseases www.cdc.gov/ncidod/dvbid/index.htm • CDC - Plague information www.bt.cdc.gov/agent/plague/index.asp Center for Food Security and Public Health Iowa State University - 2004 Acknowledgments Development of this presentation was funded by a grant from the Centers for Disease Control and Prevention to the Center for Food Security and Public Health at Iowa State University. Center for Food Security and Public Health Iowa State University - 2004 Acknowledgments Author: Radford Davis, DVM, MPH Co-author: Glenda Dvorak, DVM, MS, MPH Reviewer: Jean Gladon, BS Center for Food Security and Public Health Iowa State University - 2004
